Operator "|" not supported for types "dict[str, Unknown]" and "dict[Unknown, Unknown] | None" - is it a bug?

[Miro (miro-zamiro)]

Hi! I don't know if it is a bug, or not. But here it is.
In this repo:
https://gitlab.com/miro-zamiro/fuujin
commit: 98afc4bbee4472d4f068d5cfc9dfb7cdb77ef29c
in file fuujin/main.py there is red wave under line 8 as in this screenshot:

However, when I build the package it works as expected:

user@bonifacy ~ (main)> nix build .#fuujin && fuujin -c /home/user/Git/fuujin/test/
2026-01-01 15:20:13.628220 --> mode: manager
2026-01-01 15:20:13.628262 --> config_path: /home/user/Git/fuujin/test/
2026-01-01 15:20:13.628273 --> debug_level: 2
2026-01-01 15:20:13.628279 --> language: en
['gui_interface=true\n', 'web_interface=1']
2026-01-01 15:20:13.628435 --> native host: False
{'mode': 'manager', 'config_path': '/home/user/Git/fuujin/test/', 'debug_level': '2', 'language': 'en', 'native_host': False, 'gui_interface': True, 'web_interface': True}
user@bonifacy ~ (main)> 

[Xoriun]

Pyright compares all possible return types and in your case checks, if the operations | can be performed on them.
In the first line of the error message, Pyright tells you the possible types, which for 'variables is only dict[str, Unknown] and for the call into the fuujin library is either dict[Unknown,Unknonw] or None.
In the second line, Pyright tells you which combination of these is no supported for the operation |, in your case this is when the library call returns None.
Indeed, if this call does return None, there will be a TypeError when trying to use |.

So this error message does not mean that this will never work, but rather that there is some edgecase that was not considered.

If you know that the library call will never return None under your particular circumstances, then you can ignore it.
Otherwise consider checking if the return value of the library call is None and only if that is not the case, use |.
Then, also Pyright should not complain anymore.

[Miro (miro-zamiro)]

Thank you for your response!
Miro